1. Field of the Invention
The invention is directed to a rolling bearing, particularly a rotor bearing or main bearing for a wind power generating plant, having at least two mutually concentric rings that are separated from each other by a gap in which one or more rows of rolling elements roll along raceways on both rings, such that the two rings can be rotated in mutually opposite directions about their common axis, wherein each ring has at least one planar, annular, preferably raised connection surface for connection to a machine part, plant part, chassis or foundation, wherein the connection surfaces extend parallel to one another and are passed through approximately perpendicularly by a plurality of fastening bores for receiving fastening bolts that are inserted all the way through them or screwed into them.
2. Description of the Prior Art
Since larger machines and plants are generally more advantageous commercially than smaller ones, there has been a steady trend toward increasingly large capacities. Particularly clear evidence of this phenomenon can be seen in the steadily increasing overall size and power rating of wind power generating plants, although similar effects can also be noted elsewhere, for instance in the ever-greater size of ships and aircraft. This trend carries with it a need for increasingly large rolling bearings for such equipment. In wind power generating plants, this relates primarily to the main bearing for supporting the rotor, the yaw or nacelle bearing for pivoting the nacelle, and finally, the blade bearings for changing the pitch of the rotor blades. The blade bearings are in turn responsible for most of the strain on the main or rotor bearing, since the latter must absorb the repeated wind pressure from the blade bearings in the axial direction; it must support the entire weight of the rotor in the radial direction, including the hub and the rotor blades; and finally, it has to rotate the most constantly. Consequently, triple-row roller bearings are used preferentially as main bearings for wind power generating plants, due in particular to their much longer service life than that of other rolling bearing designs.
In all mountings where loads are transmitted across oblique contact angles, the bearings are subject to increased expansion due to the compliance of the adjacent structure. The effects can be seen in the form of greater leakage of lubricating agents, increased sliding movements by the rollers when idle, greater ovalization of the bearing rings, etc. In triple-row bearings, however, which transmit the loads to a radial raceway with a contact angle of 0° and the tilting moments and axial loads to two axial rows with a contact angle of 90°, these effects are smaller, regardless of whether rollers or balls are used as the load-transmitting elements.
Triple-row roller bearings have a relatively narrow axial clearance, however, which is troublesome particularly in wind turbine applications.
Furthermore, roller bearings are much more sensitive than ball bearings to standstill vibrations. Efforts are therefore being made to develop bearings for such applications that operate under bias as much as possible.
The axial play of the bearing can be narrowed further by the bolt clamping forces exerted on the bearing rings by the fastening bolts, and undesirably high biases can occur in the axial rows if the ring geometry is unfavorable.
To incorporate a bearing of this kind, therefore, an extremely delicate compromise must be reached among the various requirements: On the one hand, these bearings should run very smoothly; on the other hand, they should ideally be adjusted free of play. With rotor bearings several meters in diameter, such adjustment and fine-tuning of play is very labor-intensive, and even relatively small changes in environmental conditions, e.g. temperature changes, can disrupt the sensitive balance struck between freedom from play and moderate bias.
Added to this is the fact that load distributions on the individual axial raceways and the radial raceway can differ greatly, depending on the load case. For example, load situations can actually arise where an axial row is largely or completely load-free, and the rolling elements in that row do not roll sufficiently or even stand still. In this case, the rolling elements drag over the raceway and the worrisome phenomenon of flat wear can develop, particularly in the form of abrasions. From the disadvantages of the described prior art comes the problem initiating the invention: in a rolling bearing of this species, to eliminate the described disadvantages that occur particularly in the case of large bearing diameters of approximately one meter or more.